Since their initial conception approximately 10 years ago, active- matrix flat-panel imagers (AMFPIs) have undergone extensive research and development. As a result, they are on the threshold of wide- spread introduction to clinical use. While the first generation of AMFPIs offers the promise of significant benefits over existing commercially available technologies, present AMFPI technology suffers from inherent limitations which severely restrict its performance under conditions of low exposure, as is common only encountered in fluoroscopy. Specifically, existing AMFPI devices suffer from a relatively large additive noise compared to the gain of the system. This problem applies to AMFPI designs using both indirect and direct detections of the incident by x-ray radiation. Consequently, the question to be examined in the proposed research is : ~Is it feasible, though the incorporation of fundamental innovations to imager design, to develop large area, advanced technology, fluoroscopic AMFPIs capable of performance levels matching or exceeding those of x-ray image intensifiers under all conditions and capable of very high performance radiographic imaging?~ To address this question this grant application proposes an ambitious program of research to investigate a variety of innovative strategies which offer the promise of "leap--frogging" present AMFPI technology. Through the iterative development of a series of small and large area indirect and direct detection prototypes incorporating innovative strategies to significantly reduce additive noise and enhance system gain, the most promising strategies will be identified and ultimately implemented in a large area, 100 um pitch, advanced technology prototype imager. The successful conclusion of this research will facilitate the creation of a new highly advanced imaging technology allowing the realization of very high performance AMFPI systems. Such systems would offer higher spatial resolution and detective quantum efficiency (DQE) performance matching or exceeding that of existing x-ray image intensifier systems, and DQE performance superior to existing film-screen and computed radiography systems under all clinical conditions. The successful development of a technology exhibiting these performance levels could have a profound impact on digital radiology.